Ted Rossel, Plant Engineer at Veolia, explains that after the water is treated it has better quality than the original incoming canal water. Around 70% is then discharged into the local Ghent-Bruges canal, while the remaining 30% of the treated water is recycled back for reuse in the dairy plant, thus reducing demand for fresh water.
Sludge variation was causing upsets
A few years ago, the Veolia plant was experiencing difficulties with sludge dewatering that was causing process upsets and giving the operators headaches. Basically, the sludge quality and dryness following the centrifuges was inconsistent, with the variations making the sludge difficult and expensive to handle.
At that time, Veolia had a corporate purchasing agreement for chemicals that exclusively involved suppliers other than Kemira. However, although the plant did not have a formal relationship with Kemira at the time, Ted knew that Kemira had deep expertise with this type of problem and decided to get in touch.
“So,” explains Wim Smet, Kemira’s water and industry sales manager in Belgium, “one day we got a call from them asking if we could help out. Of course, even though they were not then a customer, we went over and started looking at possible solutions. After talking with Ted about the problem and examining the sludge characteristics, together we decided to try a different polymer that we had good experience with on a similar application. This worked, and quickly solved the sludge handling problem by raising the dryness consistently to 32% and reducing the variations.”
Digging deeper into COD removal possibilities
This success in solving the sludge problem led the partners to discuss another challenge at the Veolia plant: COD removal on the dissolved-air-flotation stage (DAF). At that time the COD removal in the DAF was around 60%. Ted felt higher removal was possible, and he was motivated by the fact that higher COD removal there would mean less sludge to dewater, which in turn gives financial savings in terms of polymer and electricity.
Again, Kemira and Veolia discussed the process, and possible solutions. The plant was previously using ferric chloride as a coagulant, followed by an anionic polymer for flocculation. Aiming to get better flocculation, Ted and Wim decided to experiment by replacing the anionic polymer with a special cationic polymer. The change immediately showed positive results, with the COD removal rapidly increasing to about 80%. A simple adjustment, once again, gave the plant nice benefits: Reduced polymer and electricity usage, due to less COD going to the biological treatment step.
Powered by smart process management
The positive partnership for continuous improvement has continued with several additional advances. Since Kemira is now supplying various chemicals to Veolia’s Aalter plant, a logical next step was to install the Kemira KemConnect™ VMI intelligent stock level monitoring system. KemConnect™ enables 24/7 real-time process monitoring and diagnostics for even higher process efficiency and smoother operation. With automated alerts, it also guarantees the accurate supply of chemicals, including polymers and ferric chloride.
We are always open to share our problem-solving expertise, whether or not you are currently a customer. Got questions? Get in touch!
